Why Have Humans Gotten Smaller and Weaker Since About 10,000 Years Ago, and What Factors Are Now Reversing That Trend? — Here’s What the Evidence Suggests

The modern human species, Homo sapiens, is believed to have existed for around 300,000 years, but our bodies did not always stay the same all throughout the journey. Researchers found that around 10,000 years ago, there was a more dramatic but gradual shift in our size and strength. We became smaller and weaker as a species.

Scientists believe that there were many factors affecting this trend, but there is an event in particular that may have more significance than the others. Moreover, this decline in average human size and strength is now reversing, but what exactly triggered it in the first place? And why is it reversing now? Let’s explore these questions and ideas in this article.

Why Size and Strength Declined After the Agricultural Shift

One of the major reasons for the shift in human anatomy is the change in diet and nutrition. Around 12,000 to 10,000 years ago, Homo sapiens transitioned from being hunter-gatherers for most of their existence to farming and agriculture. This shift was not instantaneous, but rather gradual, and has occurred for thousands of years.

Most people would think that the change of lifestyle to become sedentary and focus on growing our own food would result in humans being more nutritious. However, this was not the case, especially in the beginning, when our ancestors were still reliant on a few select species of wild plants and animals to farm.

In other words, the farmers back then had less nutrition in their food compared to their hunter-gatherer counterparts. This is because the lifestyle before farming allowed humans to have a more varied diet. They would hunt the animals in the wild, but also gather and eat different edible plant materials. They would also migrate to a new habitat and adapt to consume the resources readily available in these new environments.

However, when humans transitioned to become farmers, their new diet reduced the intake of necessary and helpful nutrients like proteins, minerals, and other vitamins. This is because they focused on fewer types of food that they are capable of growing, like grains. This is the trade-off of having a reliable food supply from agriculture in the early days. It meant that the humans, over time, had consumed fewer nutrients that would have allowed them to maintain the robustness of their bones or the size of their bodies.

Read more: Australian Museum

The Role of Mobility, Growth, and Genetic/Environmental Interplay

The Entire 250,000 - Year Story of Homo Sapiens | What Really Happened at 50,000?

When humans transitioned into farming, they became less mobile, and this may have also played a big role in our bodies getting weaker and smaller. First, the hunter-gatherers would constantly migrate as they are heavily reliant on what nature could provide, unlike farmers who grow their own food.

These migrations mean that they often utilize their bodies more because they would also carry heavy loads, run away from predators, or chase prey. They would also walk long distances and climb mountains and rocky settlements. On the other hand, farmers’ jobs were also not easy, but they became repetitive and less physically demanding overall. In other words, the transition from hunter-gatherers to farming reduced the evolutionary pressure for humans to be stronger and bigger.

Additionally, the environment and their new lifestyle could have also made significant contributions to this shift. When people started farming, they also needed to stay together in one place to be able to tend to the crops and animals for most of the year. It means that when a disease spreads, it does so very quickly. So, early farmers became more vulnerable to pathogens, parasites, and childhood illnesses, which could have affected their overall growth and adult strength as a group.

Why the Trend Is Now Reversing — Nutrition, Healthcare & Lifestyle

Today, in many different parts of the world, the trend of humans becoming smaller and weaker is now reversing. However, what exactly changed? Most of us are still living in one place, near each other. We grow our own food still, through farming. We are not hunter-gatherers anymore who climb mountains, chase prey, run from predators, walk long distances, and carry heavy loads while migrating. So, what could have changed this downward trend?

Scientists discovered that the very same reasons that are thought to have contributed to the shift in human anatomy in early human farmers were now less of a problem or are completely solved. During the last few centuries, humanity has more variety than ever. The nutrition in our food supplies and diet, like proteins, minerals, and vitamins, is now much higher or better than in the early days.

Moreover, our civilization is now less vulnerable to the health and diseases that the first human farmers encountered due to living closely with more people and animals. Those factors that may have impaired their growth have been solved or limited by the advances in our medical technologies.

There were also some modern lifestyle changes that could have contributed to this reversal of trends, and that is our participation in training and workouts. It is still not as strenuous and physically demanding as the lifestyle of hunter-gatherers, but it is still a lot better and healthier than the sedentary way of life of early farmers.

In short, the same flexible human body that allows us to become weaker and smaller over time is also the same one that helps us adapt to changes in our environment or lifestyle, in order to reverse the declining trend.

Read more: PubMed Central

What This Means for Human Evolution and Future Strength

The Proof That Humans Are Getting Weaker (And Dumber)

The fact that human anatomy has changed in size and strength in different parts of the world and across generations reminds us that our environment, diet, lifestyle, and challenges could shape our bodies.

Moreover, the reduction in size and strength does not necessarily mean it is a negative for our own survival. It could also help us conserve more energy and allocate it to other parts of our bodies or lifestyle. It could also be an adaptation to survive different challenges.

For example, during scarcity of resources, which were common in early agricultural societies because of crop failures and poor storage, smaller bodies would need a lot less food supply to maintain and grow. This could be an evolutionary advantage and allows individuals or groups to pass on their genes to the next generation, gradually creating a trend of declining size in body parts.

However, when conditions improved, where we are less vulnerable to diseases, more variability in nutrition in our food supply, and more deliberate training of our bodies, we could reverse the trend and start another one where we are growing stronger and bigger as a species. In other words, the human body size and strength are not fixed and will adapt and develop with us to survive.

Author's Final Thoughts

Humans got smaller and weaker after the advent of farming around 12,000 to 10,000 years ago. This is mainly because of the changes in our lifestyle, diet, and environment. The rise of agriculture gave humans a more reliable food supply, but with fewer variations. This made their resources less nutritious than their hunter-gatherer counterparts.

Additionally, living together in one place with all the other humans and animals allowed the spread of diseases to be more rapid, and may have affected their growth. Moreover, the transition to a sedentary lifestyle may have reduced the selective pressure for humans to be bigger and stronger. But, in recent times, the declining trend has been reversed, and with better healthcare, nutritious food variety, and improvement of overall lifestyle, our bodies could change once again as a species over many generations.

Read next: Why Did Our Ancestors Nearly Vanish Around 900,000 Years Ago, With Their Population Dropping to Just ~1,280 Individuals? — Here’s What Scientists Suggest

References & Further Reading

Marciniak, S., et al. (2022). An integrative skeletal and paleogenomic analysis of stature variation suggests relatively reduced health for early European farmers. Proceedings of the National Academy of Sciences (PNAS). https://doi.org/10.1073/pnas.2106743119

Ruff, C. B., et al. (2015). Gradual decline in mobility with the adoption of food production in Europe. Proceedings of the National Academy of Sciences (PNAS). https://doi.org/10.1073/pnas.1502932112

Chirchir, H., et al. (2015). Recent origin of low trabecular bone density in modern humans. Proceedings of the National Academy of Sciences (PNAS). https://doi.org/10.1073/pnas.1411696112

Larsen, C. S. (1995). Biological changes in human populations with agriculture. Annual Review of Anthropology. https://www.annualreviews.org/doi/10.1146/annurev.an.24.100195.001153

NCD Risk Factor Collaboration (NCD-RisC). (2016). A century of trends in adult human height. eLife. https://doi.org/10.7554/eLife.13410

Stock, J. T., et al. (2023). Long-term trends in human body size track regional paleoclimate. Proceedings of the National Academy of Sciences (PNAS). https://doi.org/10.1073/pnas.2209482119

Mummert, A., et al. (2011). Stature and robusticity during the agricultural transition: Evidence from across the globe. American Journal of Physical Anthropology. https://pubmed.ncbi.nlm.nih.gov/21507735/